<s>
PGPCoder	B-Application
or	O
GPCode	B-Application
is	O
a	O
trojan	O
that	O
encrypts	O
files	O
on	O
the	O
infected	O
computer	O
and	O
then	O
asks	O
for	O
a	O
ransom	O
in	O
order	O
to	O
release	O
these	O
files	O
,	O
a	O
type	O
of	O
behavior	O
dubbed	O
ransomware	O
or	O
cryptovirology	O
.	O
</s>
<s>
While	O
a	O
few	O
Gpcode	B-Application
variants	O
have	O
been	O
successfully	O
implemented	O
,	O
many	O
variants	O
have	O
flaws	O
that	O
allow	O
users	O
to	O
recover	O
data	O
without	O
paying	O
the	O
ransom	O
fee	O
.	O
</s>
<s>
The	O
first	O
versions	O
of	O
Gpcode	B-Application
used	O
a	O
custom-written	O
encryption	O
routine	O
that	O
was	O
easily	O
broken	O
.	O
</s>
<s>
Variant	O
Gpcode.ak	O
writes	O
the	O
encrypted	O
file	O
to	O
a	O
new	O
location	O
,	O
and	O
deletes	O
the	O
unencrypted	O
file	O
,	O
and	O
this	O
allows	O
an	O
undeletion	O
utility	O
to	O
recover	O
some	O
of	O
the	O
files	O
.	O
</s>
<s>
Variant	O
Gpcode.am	O
uses	O
symmetric	B-Algorithm
encryption	I-Algorithm
,	O
which	O
made	O
key	O
recovery	O
very	O
easy	O
.	O
</s>
<s>
In	O
late	O
November	O
2010	O
,	O
a	O
new	O
version	O
called	O
Gpcode.ax	O
was	O
reported	O
.	O
</s>
